This invention relates to a sheet feeding apparatus which includes a sheet advancing (traction) member provided with carrier pawls and circulating at a constant speed for conveying the sheets to a working station in which they arrive with an initial velocity which is at least as high as the circulating speed of the carrier pawls.
The traction member of the feeding apparatus may include traction chains. Material to be handled generally consists of metal sheets or strips or may be crosscut pieces. A typical working station into which the sheets are introduced comprises a roller knife cutter in which the throughput velocity remains constant and corresponds to the initial velocity. The initial velocity, in turn, with which the sheets are drawn into the working station must in no event be less than the advancing velocity, otherwise a buckling of the sheet material will occur. In practice, the initial velocity of the working station is selected to be slightly greater than that of the feeding apparatus.
Roller knife cutters sever the metal sheets, such as tin-plated iron sheets used for sheet packages, into strips in a first operation and into crosscut pieces in a second operation. Known feeding apparatus for metal sheets and also for crosscut pieces include a chain-type feeding apparatus whose circulating speed is smaller than the circumferential or intake speed of the roller knife cutter. For the parallel alignment and acceleration of the metal sheets or strips approximately to the circumferential speed of the roller knife cutter, downstream of the feeding apparatus (as viewed in the direction of material feed) a pawl feeding device with linearly reciprocating pawl pushers is arranged.
The throughput of the roller knife cutter is determined essentially by the stroke, the mode of operation and the stroke frequency of the oscillating pawl pusher drive. If, for example, the pusher drive executes seven strokes per sheet, then for a delivery of forty sheets per minute there are needed 280 strokes per minute for a stroke of approximately 100 mm. It is a disadvantage of such a prior art construction that extremely high accelerations and inertia forces may appear. The earlier-noted sheet delivery itself may be achieved only with high manufacturing precision and with sheet material which is of light weight. In any event, the pusher drive is, because of the high inertia forces, exposed to a very significant wear and also generates substantial noise.